Method and system for performing invasive medical procedures using a surgical robot

ABSTRACT

A method and system for performing invasive procedures includes a surgical robot which is controlled by a guidance system that uses time of flight calculations from RF transmitters embedded in the robot, surgical instrument, and patient anatomy. Sensors around the room detect RF transmissions emitted by the RF transmitters and drive the robot according to a preprogrammed trajectory entered into the guidance system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/542,560, filed Jul. 5, 2012, which is a continuation of U.S. patentapplication Ser. No. 11/845,557, filed Aug. 27, 2007, now U.S. Pat. No.8,219,178, which is a continuation-in-part of U.S. patent applicationSer. No. 11/838,027, filed Aug. 13, 2007, now U.S. Pat. No. 8,219,177,which is a continuation-in-part of U.S. application Ser. No. 11/676,023,filed Feb. 16, 2007, now U.S. Pat. No. 8,010,181. This application isrelated to, but does not claim priority to U.S. Provisional PatentApplication Nos. 60/775,816 and 60/774,586, both of which were filed onFeb. 16, 2006. The contents of all applications are hereby incorporatedby reference in their entireties for all purposes.

FIELD OF THE INVENTION

This invention generally relates to the use of robots in medicalprocedures and, more particularly, to a method and system of controllingthe movement of an end effectuator disposed on a robot arm by means of,for example, time of flight measurements of radio frequency (“RF”)signals that are emitted from inside a patient and that are received byat least three RF receivers positioned near where the procedure istaking place.

BACKGROUND OF THE INVENTION

Various medical procedures require the precise localization of a threedimensional position of a surgical instrument within the body in orderto effect optimized treatment. For example, some surgical procedures tofuse vertebrae require that a surgeon drill multiple holes into the bonestructure at precise locations. To achieve high levels of mechanicalintegrity in the fusing system and to balance the forces created in thebone structure it is necessary that the holes are drilled at the correctprecise location. Vertebrae, like most bone structures, have complexshapes made up of non-planar curved surfaces making precise andperpendicular drilling difficult. Conventionally, a surgeon manuallyholds and positions a drill guide tube by using a guidance system tooverlay the drill tube's position onto a three dimensional image of thebone structure. This manual process is both tedious and time consuming.The success of the surgery is largely dependent upon the dexterity ofthe surgeon who performs it.

Limited robotic assistance for surgical procedures is currentlyavailable. For example, the da Vinci medical robot system is a robotused in certain surgical applications. In the da Vinci system, the usercontrols manipulators that control a robotic actuator. The systemconverts the surgeon's gross movements into micro-movements of therobotic actuator. Although the da Vinci system eliminates hand tremorand provides the user with the ability to work through a small opening,like many of the robots commercially available today, it is expensive,obtrusive, and the setup is cumbersome. Further, for procedures such asthoracolumbar pedicle screw insertion, these conventional methods areknown to be error-prone and tedious.

One of the characteristics of the da Vinci system which makes it errorprone is that, like many of the current robots used in surgicalapplications, it uses an articular arm based on a series of rotationaljoints. The use of an articular system creates difficulties in arrivingat a precisely targeted location because the level of any error isincreased over each joint in the articular system.

SUMMARY OF INVENTION

In one embodiment, the present invention provides a surgical robot andan imaging system that utilize a Cartesian positioning system as opposedto an articular positioning system. This feature allows, for example,the movement of an effectuator element that forms or is attached to theend of a surgical robot to be individually controlled on the x, y and zaxes. This feature also allows the roll, pitch and yaw of theeffectuator element to be controlled without creating movement on the x,y or z axes.

The effectuator element can include a leading edge that is eitherbeveled or non-beveled. In an exemplary embodiment, a non-beveledeffectuator element is employed that is capable of ablating a pathwaythrough tissue to reach the target position and will not be subjected tothe mechanical forces and deflection created by a typical bevel tissuecutting system. In accordance with an exemplary embodiment, a surgicalrobot includes three linear motors that separately control movement ofthe effectuator element on the x, y and z axes. These separate motorsallow, for example, a degree of precision to be obtained that is notprovided by conventional surgical robots. This aspect of the inventiongives the surgeon the capability of exactly determining position andstrike angles on a three dimensional image.

Another exemplary aspect of the present invention involves the use of atleast one RF transmitter that is mounted on an effectuator element ofthe surgical robot or on a medical instrument that is held by theeffectuator element. Three or more RF receivers are mounted in thevicinity of the surgical robot. The precise location of the RFtransmitter and, therefore, the surgical instrument formed or held bythe end effectuator can be precisely determined by analyzing the RFsignals that are emitted from the RF transmitter. By measuring the timeof flight of the RF signal from the transmitter to the RF receivers thatare positioned at known locations, the position of the end effectuatorelement with respect to a patient can be determined. A doctor or surgeoncan utilize this aspect of the present invention to, for example,perform epidural injections of steroids into a patient to alleviate backpain without the use of x-rays as is currently done with x-rayfluoroscopic techniques.

A still further exemplary aspect of the present invention involves theuse of RF feedback to actively control the movement of a surgical robot.To do this control, RF signals are sent by the RF transmitter on aniterative basis and then analyzed in an iterative process to allow, forexample, the surgical robot to automatically move the effectuatorelement to a desired location within a patient's body. The location ofthe effectuator element and surgical instrument are dynamically updatedand can be, for example, displayed to a user in real-time.

The present invention also contemplates a system where RF transmittersare disposed on other elements of the surgical robot, or anywhere withinthe room where the invasive procedure is taking place, in order to trackother devices.

The present invention also contemplates a system where RF transmittersare disposed on the anatomical part of the patient that is the target ofthe invasive procedure. This system can be used, for example, to correctthe movement of the surgical robot in the event the anatomical targetmoves during the procedure.

In one embodiment, the present invention contemplates a new mechanicalsystem, new component development and improved imaging methods designedwith an integrated software architecture that would combine imageguidance, medical imaging and a robotic positioning system.

The current invention also contemplates a system that will automaticallyposition and rigidly hold, for example, a guide tube that is preciselyaligned with the required trajectory of a pedicle screw during pediclescrew insertion procedures.

BRIEF DESCRIPTION OF THE DRAWINGS

The benefits and advantages of the present invention will become morereadily apparent to those of ordinary skill in the relevant art afterreviewing the following detailed description and accompanying drawings,wherein:

FIG. 1 is a partial perspective view of a room in which an invasivemedical procedure is taking place by means of a surgical robot themovement of which is controlled by analysis of RF signals that areemitted from an inside the patent and received by RF receivers mountedtherein;

FIG. 2 is a perspective view of a surgical robot according to anembodiment of the present invention;

FIGS. 3A & 3B are perspective views of the surgical robot illustrated inFIG. 2, which show the movement of the base of the surgical robot in thez-axis direction;

FIG. 4 is a partial perspective view of the surgical robot of FIG. 2which shows how the robot arm can be moved in the x-axis direction;

FIGS. 5A & 5B are partial perspective views of the surgical robot ofFIG. 2, which show how the robot arm can be moved in the y-axisdirection;

FIG. 6 is a perspective view of a portion of the robot arm of FIG. 2showing how an effectuator element can be twisted about a y-axis;

FIG. 7 is a perspective view of a portion of a robot arm of FIG. 2showing how an effectuator element can be pivoted about a pivot axisthat is perpendicular to the y-axis;

FIGS. 8A & 8B are partial perspective views of the surgical robot ofFIG. 2, which show the movement of a surgical instrument along thez-axis from an effectuator element;

FIG. 9 is a system diagram of which shows the local positioning sensors,controlling PC, and Radiofrequency (RF) transmitter;

FIG. 10 is a system diagram of the controlling PC, user input, andmotors for controlling the robot;

FIG. 11 is a flow chart diagram for general operation of the surgicalrobot according to an embodiment of the present invention;

FIG. 12 is a flow chart diagram for a closed screw/needle insertionaccording to an embodiment of the present invention;

FIG. 13 is a flow chart diagram of a safe zone surgery according to anembodiment of the present invention;

FIG. 14 is a flow chart diagram of a flexible catheter insertionprocedure according to an embodiment of the present invention;

FIG. 15A shows a screenshot of a monitor display showing a set up of theanatomy in X, Y and Z views according to an embodiment of the presentinvention;

FIG. 15B shows a screenshot of a monitor display showing what the userviews during an invasive procedure according to an embodiment of thepresent invention;

FIG. 16 shows the use of a calibration frame with the guidance systemaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describeda presently preferred embodiment with the understanding that the presentdisclosure is to be considered an exemplification of the invention andis not intended to limit the invention to the specific embodimentillustrated. It should be further understood that the title of thissection of this specification, namely, “Detailed Description Of TheInvention”, relates to a requirement of the United States Patent Office,and does not imply, nor should be inferred to limit the subject matterdisclosed herein.

Referring now to FIG. 1, it is seen that in one embodiment of thesurgical robot system, a room 10 where an invasive procedure isoccurring includes a surgical robot 15, a patient 18 and positioningsensors 12 is provided. Surgical robot 15 includes a display means 29,and a housing 27 which contains a robot arm 23. Robot arm 23 is attachedto end effectuator 30. In one embodiment, surgical instrument 35 isremovably attached to end effectuator 30. In another embodiment, the endeffectuator 30 itself forms an instrument that is used to allow aninvasive procedure to take place.

In an embodiment of the invention, prior to an invasive procedure, a 3Dimage scan is taken of the desired surgical area of patient 18 and sentto a computer (not shown) in communication with surgical robot 15. Aphysician then programs a desired point of insertion and trajectory forsurgical instrument 35 to reach the desired anatomical target in patient18. This desired point of insertion and trajectory is planned on the 3Dimage scan which is displayed on display means 29. For example, aphysician can plan the desired insertion point and trajectory on acomputed tomography (CT) scan of patient 18.

One aspect of the present invention involves the use of a localpositioning system (LPS) to track the position of surgical instrument35. A general description of the LPS system follows. An RF transmitteris affixed at a known location on either the end effectuator 30 or themedical instrument 35. Three transmitters may be evenly radiallydistributed around the effectuator 30. Three or more RF receivers arepositioned at known locations within, for example, the room where theinvasive procedure is to take place. Preferably, the RF receivers arenot located in the same plane that is parallel to the floor of the roomwhere the procedure is performed.

To calculate the position of the RF transmitter, the time of flight ofthe RF signal from the RF transmitter to each one of the RF receivers ismeasured. Because the velocity of the RF signal is known, the time offlight measurements result in at least three distance measurements, onefrom each RF receiver.

The memory of a control device that performs the time of flightcalculations can include, for example, a geometrical description of thelocation of the RF transmitter with respect to the operative end of themedical instrument 35 or end effectuator 30 that is utilized to performor assist in performing an invasive procedure. By doing so, the positionof the RF transmitter as well as the dimensional profile of the medicalinstrument or the effectuator element itself can be displayed on amonitor that is viewed by the person performing the invasive procedure.As one example, the end effectuator element 30 can be a tubular elementthat is positioned at a desired location with respect to, for example, apatient's spine in connection with the performance of a spinal surgery.The tubular element can be aligned with the z axis defined bycorresponding robot motor or, for example, can be disposed at an anglerelative thereto. In either case, the control device takes theorientation of the tubular element and the position of the RFtransmitter into account. The transmitter is affixed at a desiredlocation of the instrument and the control device may be configured toselectively energize the transmitter to cause at least a portion of theinstrument to move in a desired direction.

Another aspect of the present invention involves the utilization of arobot that is capable of moving the end effectuator 30 in x, y and zdirections that are orthogonal to each other independently of each otheror in any combination. For example, the end effectuator 30 can be moveda given distance along the x axis without causing any movement along they or z axes. The roll, pitch and yaw and the end effectuator 30 also canbe selectively controlled. This aspect of the present invention isadvantageous because, for example, its use allows invasive medicalprocedures to take place with a significantly improved accuracy comparedto conventional robots that utilize, for example, a six degree offreedom robot arm. A more complete description of these and otheraspects of the invention follows.

Referring to FIG. 1, positioning sensors 12 receive RF signals from RFtransmitters (not pictured) located within room 10. These RFtransmitters are disposed on various points on surgical robot 10 and/oron patient 18. For example, RF transmitters are attached to housing 27,robot arm 23, end effectuator 30 and surgical instrument 35. Positioningsensors 12, which in an exemplary embodiment comprise RF receivers thatare in communication with a computer (not pictured), receive the signalfrom the RF transmitters. Each transmitter transmits on a differentfrequency so the identity of each transmitter in the room isdeterminable. The location of the RF transmitters, and consequently theobjects to which the transmitters are attached, are calculated by thecomputer using time of flight algorithms.

The computer (not pictured) is also in communication with surgical robot15, and moves surgical robot 15 according to the preplanned trajectoryentered prior to the procedure. The position of surgical instrument 35is dynamically updated so that surgical robot 15 is aware of thelocation of surgical instrument 35 location at all times during theprocedure. Consequently, surgical robot 15 can move surgical instrument35 to the desired position quickly with minimal damage to patient 18 andwithout any further assistance from a physician unless the physician sodesires. Surgical robot 15 can also correct the path if surgicalinstrument 35 strays from the desired trajectory.

The physician or other user of the system has the option to stop,modify, or manually control the autonomous movement of surgical robot15. Further, tolerance controls are preprogrammed into surgical robot15, which adjust the movement of the surgical robot 15 if certainconditions are met. For example, if the surgical robot 15 cannot detectthe positions of surgical instrument 35 because of a malfunction in theRF transmitter attached thereto, it will stop movement. Another exampleis if surgical robot 15 detects a resistance above a tolerance level,then it will stop movement.

In a preferred embodiment of the invention, display means 29 is amonitor attached to surgical robot 15. Alternatively, display means 29is not attached to surgical robot 15, but is located either withinsurgical room 10 or in a remote location.

The computer for use in the system (not pictured), can be located withinsurgical robot 15, or, alternatively, in another location withinsurgical room 10 or in a remote location. The computer is inconununication with positioning sensors 12 and surgical robot 15.

The surgical robot can also be used with existing guidance systems.Alternative guidance systems are within the scope and spirit of theinvention. For instance, an optical tracking system for tracking thelocation of the surgical device. A commercially available infraredoptical tracking system, such as Optotrak (Northern Digital, Waterloo,Ontario, Canada), can be used to track the patient movement and therobot's base location and used with the guidance system. Optical systemsrequire the use of optical markers, which are markers which emit orreflect light, attached to the surgical device. Light emitted from themarkers is read by cameras or optical sensors. The location of theobject is calculated through triangulation.

Referring now to FIG. 2, it is seen that one embodiment of the surgicalrobot is shown. The surgical robot includes a base 25 connected towheels 31. Case 40 is slidably attached to base 25 so that case 40 canslide up and down on a z-axis line perpendicular to the surface on whichbase 25 sits. Surgical robot also includes a display means 29, and ahousing 27 which contains arm 23. Arm 23 is connected to an endeffectuator 30. Surgical instrument 35 is removably attached to endeffectuator 30.

Surgical instrument 35 can be any instrument used in a medicalprocedure, both invasive or non-invasive. Surgical instrument 35 may be,for example, a catheter, a probe, a sensor, needle, scalpel forceps, orany other instrument used in a surgical, non-invasive, or diagnosticprocedure. Surgical instrument 35 can also be a biological deliverydevice apparatus, such as a syringe, which can distribute biologicallyacting compounds throughout the body. The plunger of the syringe may bemanually pressed by a user or automatically compressed by the systemonce the desired target is reached.

The surgical robot is moveable in a plurality of axes in order toimprove the ability to precisely reach a target location. The robotmoves on a Cartesian positioning system, that is, movements in differentaxes can occur relatively independently instead of at the end of aseries of joints.

Referring now to FIGS. 3A and 3B, the movement of case 40 relative tobase 25 is shown. Case 40 can raise and lower relative to the base 25 inthe z-axis direction.

In a preferred embodiment of the invention, housing 27 is attached tocase 40 and moves in the z-direction with case 40 when case 40 is raisedand lowered. Consequently, arm 23, end effectuator 30 and surgicalinstrument 35 move with case 40 as case 40 is raised and loweredrelative to base 25.

Referring now to FIG. 4, housing 27 is slidably attached to case 40 sothat it can extend and retract in a x-axis direction relative to case 40and perpendicular to the direction case 40 moves relative to base 25.Consequently, arm 23, end effectuator 30 and surgical instrument 35 movewith housing 27 as housing 27 is extended and retracted relative to case40.

Referring now to FIGS. 5A and 5B, the extension of arm 23 along they-axis is shown. Ann 23 is extendable on the y-axis relative to case 40,base 25, and housing 27. Consequently, end effectuator 30 and surgicalinstrument 35 move with arm 23 as arm 23 is extended and retractedrelative to housing 27. In an embodiment of the invention, arm 23 isattached to a low profile rail system (not shown) which is encased byhousing 27.

Referring now to FIGS. 6, 7 and 8, the movement of the end effectuator30 is shown. FIG. 6 shows end effectuator 30 is capable of rotatingalong the x axis. FIG. 7 shows end effectuator 30 is capable of rotatingalong the y-axis. FIG. 8 shows end effectuator 30 is capable of raisingand lowering surgical instrument 35 on the z axis.

Referring now to FIG. 9, a system diagram of the positioning sensors110, computer 100, and RF transmitters 120 is provided. Computer 100 isin communication with positioning sensors 110. In operation, RFtransmitters 120 are attached to various points on the surgical robot.RF transmitters 120 may also be attached to various points on or aroundthe anatomical target. Computer 100 sends a signal through a wiredconnection to RF transmitters 120, prompting RF transmitters 120 totransmit RF signals. The RF signals are read by positioning sensors 110.Positioning sensors 110 are in communication with computer 100, whichcalculates the location of the positions of all the RF sensors based ontime-of-flight information received from the positioning sensors 110.Computer 100 dynamically updates the calculated location of the surgicaldevice being used in the procedure, which is displayed to the user.

Alternatively, computer 100 can be wirelessly connected to RFtransmitters 120.

Referring now to FIG. 10, a system diagram of computer 100, display 150,user input 170, and motors 160 is provided. Motors 160 are installed inthe surgical robot and control the movement of the surgical robot asdescribed above. Computer 100, which dynamically updates the location ofthe surgical device being used in the procedure, sends the appropriatesignals to the motors 160 so that surgical robot reacts accordingly inresponse to information received by computer 100. For example, computer100 prompts motors 160 to move the surgical device along a preplannedtrajectory.

The user uses input 170 to plan the trajectory of the desired navigationprior to the invasive procedure. If the user wants to make changes inthe invasive procedure after it has commenced, he can use user input 170to make the desired changes. Computer 100 will then send the appropriatesignals to motors 160 in response to the user input.

In a preferred embodiment of the invention, motors 160 are pulse motorsproviding direct drive, or driving a belt drive and pulley combinationattached to the surgical instrument used in the procedure.Alternatively, motors 160 are pulse motors and are attached to a beltdrive rack-and-pinion system, or similar power transmission components.

Referring now to FIG. 11, a flow chart diagram for general operation ofthe robot according to an embodiment of the invention is shown.

At step 210, the local positioning system (LPS) establishes a spatialcoordinate measuring system for the room where the invasive procedure isto occur; in other words, the LPS is calibrated. In order to calibratethe LPS, a mechanical fixture that includes a plurality of calibratingtransmitters attached thereto is placed within the room wherepositioning sensors are located. At least three calibrating transmittersare required, but any number of calibrating transmitters above three iswithin the scope of the invention. Also, at least three positioningsensors are required, but any number of positioning sensors above threeis also within the scope of the invention, and the accuracy of thesystem is increased with the addition of more positioning sensors.

The distance between each of the calibrating transmitters relative toeach other is measured prior to calibration step 210. Each calibratingtransmitter transmits RF signals on a different frequency so thepositioning sensors can determine which transmitter emitted a particularRF signal. The signal of each of these transmitters is received bypositioning sensors. Since the distance between each of the calibratingtransmitters is known, and the sensors can identify the signals fromeach of the calibrating transmitters based on the known frequency, thepositioning sensors are able to calculate, using time of flightcalculation, the spatial distance of each of the positioning sensorsrelative to each other. The system is now calibrated. As a result, thepositioning sensors can now determine the spatial position of any new RFtransmitter introduced into the room relative to the positioningsensors.

At step 220, a 3D anatomical image scan, such as a CT scan, is taken ofthe anatomical target. Any 3D anatomical image scan may be used with thesurgical robot and is within the scope of the present invention.

At step 230, the positions of the RF transmitters tracking theanatomical target are read by positioning sensors. These transmittersidentify the initial position of the anatomical target and any changesin position during the procedure.

If any RF transmitters must transmit through a medium that changes theRF signal characteristics, then the system will compensate for thesechanges when determining the transmitter's position.

At step 240, the positions of the transmitters on the anatomy arecalibrated relative to the LPS coordinate system. In other words, theLPS provides a reference system, and the location of the anatomicaltarget is calculated relative to the LPS coordinates. To calibrate theanatomy relative to the LPS, the positions of transmitters affixed tothe anatomical target are recorded at the same time as positions oftemporary transmitters on precisely known landmarks on the anatomy thatcan also be identified on the anatomical image. This calculation isperformed by a computer.

At step 250, the positions of the RF transmitters that track theanatomical target are read. Since the locations of the transmitters onthe anatomical target have already been calibrated, the system caneasily determine if there has been any change in position of theanatomical target.

At step 260, the positions of the transmitters on the surgicalinstrument are read. The transmitters may be located on the surgicalinstrument itself, and/or there may be transmitters attached to variouspoints of the surgical robot.

In an embodiment of the invention, the surgical robot also includes aplurality of position encoders attached thereto that help determine theposition of the surgical instrument. Position encoders are devices usedto generate an electronic signal that indicates a position or movementrelative to a reference position. There are many ways to generate aposition signal, including for example, magnetic sensors, capacitivesensors, and optical sensors.

Position data read from the position encoders may be used to determinethe position of the surgical instrument used in the procedure, and maybe redundant of position data calculated from RF transmitters located onthe surgical instrument. Therefore, position data from the positionencoders may be used to double-check the position being read from theLPS.

At step 270, the coordinates of the positions of the transmitters on thesurgical instrument, and/or the positions read from the positionencoders, is calibrated relative to the anatomical coordinate system. Inother words, the position data of the surgical instrument issynchronized into the same coordinate system as the anatomy. Thiscalculation is performed automatically by the computer since thepositions of the transmitters on the anatomical target and the positionsof the transmitters on the surgical instrument are in the samecoordinate system and the positions of the transmitters on theanatomical target are already calibrated relative to the anatomy.

At step 280, the computer superimposes a representation of the locationcalculated in step 270 of the surgical device on the 3D anatomical imageof the patient taken in step 220. The superimposed image is displayed tothe user.

At step 290, the computer sends the appropriate signals to the motors todrive the surgical robot. If the user preprogrammed a trajectory, thenthe robot is driven so that the surgical instrument follows thepreprogrammed trajectory if there is no further input from the user. Ifthere is user input, then the computer drives the robot in response tothe user input.

At step 295, the computer determines whether the procedure has beencompleted. If the procedure has not been completed, then the processbeginning at step 250 is repeated.

At any time during the procedure, certain fault conditions may cause thecomputer to interrupt the program and respond accordingly. For instance,if the signal from the RF transmitters cannot be read, then the computermay be programmed to stop the movement of the robot or remove thesurgical instrument from the patient. Another example of a faultcondition is if the robot encounters a resistance above a preprogrammedtolerance level. Another example of a fault condition is if the RFtransmitters on the anatomical target indicate that the location of theanatomical target has shifted relative to the RF transmitters—thisspatial relationship should be fixed. In this case, one indicator thatthe anatomical target location has shifted relative to the transmittersis if the computer calculates that the surgical instrument appears to beinside bone when no drilling or penetration is actually occurring.

The proper response to each condition may be programmed into the, or aspecific response may be user-initiated as well. For example, thecomputer may determine that in response to an anatomy shift, the anatomywould have to be recalibrated, and the process beginning at step 230should be repeated. Alternatively, a fault condition may require theflowchart to repeat from step 210. Another alternative is the user maydecide that recalibration from step 230 is desired, and initiate thatstep himself.

Referring now to FIG. 12, a flow chart diagram for a closed screw/needleinsertion procedure according to an embodiment of the invention isshown. In a closed pedicle screw insertion procedure, the robot holds aguide tube adjacent to the patient in the correct angular orientationand at the point where a pedicle screw is to be inserted through thetissue and into the bone of the patient.

The distance between each of the calibrating transmitters relative toeach other is measured prior to calibration step 300. Each calibratingtransmitter transmits RF signals on a different frequency so thepositioning sensors can determine which transmitter emitted a particularRF signal. The signal of each of these transmitters is received bypositioning sensors. Since the distance between each of the calibratingtransmitters is known, and the sensors can identify the signals fromeach of the calibrating transmitters based on the known frequency, thepositioning sensors are able to calculate, using time of flightcalculation, the spatial distance of each of the positioning sensorsrelative to each other. The system is now calibrated. As a result, thepositioning sensors can now determine the spatial position of any new RFtransmitter introduced into the room relative to the positioningsensors.

At step 310, a 3D anatomical image scan, such as a CT scan, is taken ofthe anatomical target. Any 3D anatomical image scan may be used with thesurgical robot and is within the scope of the present invention.

At step 320, the operator selects a desired trajectory and insertionpoint of the surgical instrument on the anatomical image captured atstep 310. This desired trajectory and insertion point is programmed intothe computer so that the robot can drive a guide tube automatically tofollow the trajectory.

At step 330, the positions of the RF transmitters tracking theanatomical target are read by positioning sensors. These transmittersidentify the initial position of the anatomical target and any changesin position during the procedure.

If any RF transmitters must transmit through a medium that changes theRF signal characteristics, then the system will compensate for thesechanges when determining the transmitter's position.

At step 340, the positions of the transmitters on the anatomy arecalibrated relative to the LPS coordinate system. In other words, theLPS provides a reference system, and the location of the anatomicaltarget is calculated relative to the LPS coordinates. To calibrate theanatomy relative to the LPS, the positions of transmitters affixed tothe anatomical target are recorded at the same time as positions oftemporary transmitters on precisely known landmarks on the anatomy thatcan also be identified on the anatomical image. This calculation isperformed by a computer.

At step 350, the positions of the RF transmitters that track theanatomical target are read. Since the locations of the transmitters onthe anatomical target have already been calibrated, the system caneasily determine if there has been any change in position of theanatomical target.

At step 360, the positions of the transmitters on the surgicalinstrument are read. The transmitters may be located on the surgicalinstrument itself, and/or there may be transmitters attached to variouspoints of the surgical robot.

In an embodiment of the invention, the surgical robot also includes aplurality of position encoders attached thereto that help determine theposition of the surgical instrument. Position encoders are devices usedto generate an electronic signal that indicates a position or movementrelative to a reference position. There are many ways to generate aposition signal, including for example, magnetic sensors, capacitivesensors, and optical sensors.

Position data read from the position encoders may be used to determinethe position of the surgical instrument used in the procedure, and maybe redundant of position data calculated from RF transmitters located onthe surgical instrument. Therefore, position data from the positionencoders may be used to double-check the position being read from theLPS.

At step 370, the coordinates of the positions of the transmitters on thesurgical instrument, and/or the positions read from the positionencoders, is calibrated relative to the anatomical coordinate system. Inother words, the position data of the surgical instrument issynchronized into the same coordinate system as the anatomy. Thiscalculation is performed automatically by the computer since thepositions of the transmitters on the anatomical target and the positionsof the transmitters on the surgical instrument are in the samecoordinate system and the positions of the transmitters on theanatomical target are already calibrated relative to the anatomy.

At step 380, the computer superimposes a representation of the locationcalculated in step 370 of the surgical device on the 3D anatomical imageof the patient taken in step 310. The superimposed image is displayed tothe user.

At step 390, the computer determines whether the guide tube is in thecorrect orientation and position to follow the trajectory planned atstep 320. If it is not, then step 393 is reached. If it is in thecorrect orientation and position to follow the trajectory, then step 395is reached.

At step 393, the computer determines what adjustments it needs to makein order to make the guide tube follow the preplanned trajectory. Thecomputer sends the appropriate signals to drive the motors in order tocorrect the movement of the guide tube.

At step 395, the computer determines whether the procedure has beencompleted. If the procedure has not been completed, then the processbeginning at step 350 is repeated.

At any time during the procedure, certain fault conditions may cause thecomputer to interrupt the program and respond accordingly. For instance,if the signal from the RF transmitters cannot be read, then the computermay be programmed to stop the movement of the robot or lift the guidetube away from the patient. Another example of a fault condition is ifthe robot encounters a resistance above a preprogrammed tolerance level.Another example of a fault condition is if the RF transmitters on theanatomical target indicate that the location of the anatomical targethas shifted relative to the RF transmitters—this spatial relationshipshould be fixed. In this case, one indicator that the anatomical targetlocation has shifted relative to the transmitters is if the computercalculates that the surgical instrument appears to be inside bone whenno drilling or penetration is actually occurring.

The proper response to each condition may be programmed into the, or aspecific response may be user-initiated as well. For example, thecomputer may determine that in response to an anatomy shift, the anatomywould have to be recalibrated, and the process beginning at step 330should be repeated. Alternatively, a fault condition may require theflowchart to repeat from step 300. Another alternative is the user maydecide that recalibration from step 330 is desired, and initiate thatstep himself.

Referring now to FIG. 13, a flow chart diagram for a safe zone surgicalprocedure according to an embodiment of the invention is shown. In asafe zone surgical procedure, there is a defined “safe zone” around thesurgical area within which the surgical device must stay. The physicianmanually controls the surgical device that is attached to the endeffectuator of the surgical robot. If the physician moves the surgicaldevice outside of the safe zone, then the surgical robot stiffens thearm so that the physician cannot move the instrument in any directionthat The distance between each of the calibrating transmitters relativeto each other is would move the surgical device outside the safe zone.

The distance between each of the calibrating transmitters relative toeach other is measured prior to calibration step 400. Each calibratingtransmitter transmits RF signals on a different frequency so thepositioning sensors can determine which transmitter emitted a particularRF signal. The signal of each of these transmitters is received bypositioning sensors. Since the distance between each of the calibratingtransmitters is known, and the sensors can identify the signals fromeach of the calibrating transmitters based on the known frequency, thepositioning sensors are able to calculate, using time of flightcalculation, the spatial distance of each of the positioning sensorsrelative to each other. The system is now calibrated. As a result, thepositioning sensors can now determine the spatial position of any new RFtransmitter introduced into the room relative to the positioningsensors.

At step 410, a 3D anatomical image scan, such as a CT scan, is taken ofthe anatomical target. Any 3D anatomical image scan may be used with thesurgical robot and is within the scope of the present invention.

At step 420, the operator inputs a desired safe zone on the anatomicalimage taken in step 410. In an embodiment of the invention, the operatoruses an input to the computer to draw a safe zone on a CT scan taken ofthe patient in step 410.

At step 430, the positions of the RF transmitters tracking theanatomical target are read by positioning sensors. These transmittersidentify the initial position of the anatomical target and any changesin position during the procedure.

If any RF transmitters must transmit through a medium that changes theRF signal characteristics, then the system will compensate for thesechanges when determining the transmitter's position.

At step 440, the positions of the transmitters on the anatomy arecalibrated relative to the LPS coordinate system. In other words, theLPS provides a reference system, and the location of the anatomicaltarget is calculated relative to the LPS coordinates. To calibrate theanatomy relative to the LPS, the positions of transmitters affixed tothe anatomical target are recorded at the same time as positions oftemporary transmitters on precisely known landmarks on the anatomy thatcan also be identified on the anatomical image. This calculation isperformed by a computer.

At step 450, the positions of the RF transmitters that track theanatomical target are read. Since the locations of the transmitters onthe anatomical target have already been calibrated, the system caneasily determine if there has been any change in position of theanatomical target.

At step 460, the positions of the transmitters on the surgicalinstrument are read. The transmitters may be located on the surgicalinstrument itself; and/or there may be transmitters attached to variouspoints of the surgical robot.

In an embodiment of the invention, the surgical robot also includes aplurality of position encoders attached thereto that help determine theposition of the surgical instrument. Position encoders are devices usedto generate an electronic signal that indicates a position or movementrelative to a reference position. There are many ways to generate aposition signal, including for example, magnetic sensors, capacitivesensors, and optical sensors.

Position data read from the position encoders may be used to determinethe position of the surgical instrument used in the procedure, and maybe redundant of position data calculated from RF transmitters located onthe surgical instrument. Therefore, position data from the positionencoders may be used to double-check the position being read from theLPS.

At step 470, the coordinates of the positions of the transmitters on thesurgical instrument, and/or the positions read from the positionencoders, is calibrated relative to the anatomical coordinate system. Inother words, the position data of the surgical instrument issynchronized into the same coordinate system as the anatomy. Thiscalculation is performed automatically by the computer since thepositions of the transmitters on the anatomical target and the positionsof the transmitters on the surgical instrument are in the samecoordinate system and the positions of the transmitters on theanatomical target are already calibrated relative to the anatomy.

At step 480, the computer superimposes a representation of the locationcalculated in step 470 of the surgical device on the 3D anatomical imageof the patient taken in step 410. The superimposed image is displayed tothe user.

At step 490, the computer determines whether the surgical deviceattached to the end effectuator of the surgical robot is within aspecified range of the safe zone boundary, for example, within 1millimeter of reaching the safe zone boundary. If the end effectuator isalmost to the boundary, then step 493 is reached. If it is well withinthe safe zone boundary, then step 495 is reached.

At step 493, the computer stiffens the arm of the surgical robot in anydirection that would allow the user to move the surgical device closerto the safe zone boundary.

At step 495, the computer determines whether the procedure has beencompleted. If the procedure has not been completed, then the processbeginning at step 450 is repeated.

At any time during the procedure, certain fault conditions may cause thecomputer to interrupt the program and respond accordingly. For instance,if the signal from the RF transmitters cannot be read, then the computermay be programmed to stop the movement of the robot or remove thesurgical instrument from the patient. Another example of a faultcondition is if the robot encounters a resistance above a preprogrammedtolerance level. Another example of a fault condition is if the RFtransmitters on the anatomical target indicate that the location of theanatomical target has shifted relative to the RF transmitters—thisspatial relationship should be fixed. In this case, one indicator thatthe anatomical target location has shifted relative to the transmittersis if the computer calculates that the surgical instrument appears to beinside bone when no drilling or penetration is actually occurring.

The proper response to each condition may be programmed into the, or aspecific response may be user-initiated as well. For example, thecomputer may determine that in response to an anatomy shift, the anatomywould have to be recalibrated, and the process beginning at step 430should be repeated. Alternatively, a fault condition may require theflowchart to repeat from step 400. Another alternative is the user maydecide that recalibration from step 430 is desired, and initiate thatstep himself.

Referring now to FIG. 14, a flow chart diagram for a flexible catheteror wire insertion procedure according to an embodiment of the inventionis shown. Catheters are used in a variety of medical procedures todeliver medicaments to a specific site in a patient's body. Often,delivery to a specific location is needed so a targeted diseased areacan then be treated. Sometimes instead of inserting the catheterdirectly, a flexible wire is first inserted, over which the flexiblecatheter can be slid.

The distance between each of the calibrating transmitters relative toeach other is measured prior to calibration step 500. Each calibratingtransmitter transmits RF signals on a different frequency so thepositioning sensors can determine which transmitter emitted a particularRF signal. The signal of each of these transmitters is received bypositioning sensors. Since the distance between each of the calibratingtransmitters is known, and the sensors can identify the signals fromeach of the calibrating transmitters based on the known frequency, thepositioning sensors are able to calculate, using time of flightcalculation, the spatial distance of each of the positioning sensorsrelative to each other. The system is now calibrated. As a result, thepositioning sensors can now determine the spatial position of any new RFtransmitter introduced into the room relative to the positioningsensors.

At step 510, reference needles that contain the RF transmitters areinserted into the body. The purpose of these needles is to trackmovement of key regions of soft tissue that will deform during theprocedure or with movement of the patient.

Step 520, a 3D anatomical image scan, such as a CT scan, is taken of theanatomical target. Any 3D anatomical image scan may be used with thesurgical robot and is within the scope of the present invention. Theanatomical image capture area includes the tips of the reference needlesso that their transmitters' positions can be determined relative to theanatomy

At step 530, the RF signals from the catheter tip and reference needlesare read.

At step 540, the position of the catheter tip is calculated. Because theposition of the catheter tip relative to the reference needles and thepositions of the reference needles relative to the anatomy are known,the computer can calculate the position of the catheter tip relative tothe anatomy.

At step 550, the superimposed catheter tip and the shaft representationis displayed on the anatomical image taken in step 520.

At step 560, the computer determines whether the catheter tip isadvancing toward the anatomical target. If it is not moving to theanatomical target, then step 563 is reached. If it is correctly moving,then step 570 is reached.

At step 563, the robot arm is adjusted to guide the catheter tip in thedesired direction. If the anatomy needs to be calibrated, then theprocess beginning at step 520 is repeated. If the anatomy does not needto be recalibrated, then the process beginning at step 540 is repeated.

At step 570, the computer determines whether the procedure has beencompleted. If the procedure has not been completed, then the processbeginning at step 540 is repeated.

At any time during the procedure, certain fault conditions may cause thecomputer to interrupt the program and respond accordingly. For instance,if the signal from the RF transmitters cannot be read, then the computermay be programmed to stop the movement of the robot or remove theflexible catheter from the patient. Another example of a fault conditionis if the robot encounters a resistance above a preprogrammed tolerancelevel. Another example of a fault condition is if the RF transmitters onthe anatomical target indicate that the location of the anatomicaltarget has shifted relative to the RF transmitters—this spatialrelationship should be fixed. In this case, one indicator that theanatomical target location has shifted relative to the transmitters isif the computer calculates that the surgical instrument appears to beinside bone when no drilling or penetration is actually occurring.

The proper response to each condition may be programmed into the, or aspecific response may be user-initiated as well. For example, thecomputer may determine that in response to an anatomy shift, the anatomywould have to be recalibrated, and the process beginning at step 520should be repeated. Alternatively, a fault condition may require theflowchart to repeat from step 500. Another alternative is the user maydecide that recalibration from step 520 is desired, and initiate thatstep himself.

Referring now to FIGS. 15A & 15B, screenshots of software for use withan embodiment of the invention is provided. The software provides themethod to select the target area of surgery, plan the surgical path,check the planned trajectory of the surgical path, synchronize themedical images to the positioning system and precisely control thepositioning system during surgery. The surgical positioning system andnavigation software includes an optical guidance system or RF LocalPositioning System (RF-LPS), which are in communication with thepositioning system.

FIG. 15A shows a screen shot 600 of the selection step for a user usingthe software program. Screen shot 600 includes windows 615, 625, and635, which show a 3D anatomical image of surgical target 630 ondifferent planes. In this step, the user selects the appropriate 3Dimage corresponding to anatomical location of where the procedure willoccur. The user uses a graphic control to change the perspective of theimage in order to more easily view the image from different angles. Theuser can view the surgical target 630 separate coordinate views for eachof the X, Y and Z axis for each anatomical location in the database ineach window 615, 625 and 635, respectively.

After selecting the desired 3D image of the surgical target 630, theuser will plan the appropriate trajectory on the selected image. Aninput control is used with the software in order to plan the trajectoryof the surgical instrument. In one embodiment of the invention, theinput control is in the shape of a biopsy needle for which the user canplan a trajectory.

FIG. 15B shows a screen shot 650 during the medical procedure. The usercan still view the anatomical target 630 in different x, y and zcoordinate views on windows 615, 625, and 635.

In screen shot 650, the user can see the planned trajectory line 670 inmultiple windows 615 and 625. The actual trajectory and location of thesurgical instrument 660 is superimposed on the image. The actualtrajectory and location of the surgical instrument 660 is dynamicallyupdated and displayed.

As described earlier, the surgical robot can be used with alternateguidance systems other than an LPS. One embodiment of the inventioncontemplates the use of a calibration frame for use with the guidancesystem, as shown in FIG. 16. A calibration frame 700 can be used inconnection with many invasive procedures; for example, it can be used inthoracolumbar pedicle screw insertion in order to help achieve a moreaccurate trajectory position.

The use of the calibration frame 700 simplifies the calibrationprocedure. The calibration frame 700 comprises a combination ofradio-opaque markers 730 and infrared, or “active”, markers 720. Theradio-opaque markers 730 are located within the CT scan region 710, andthe active markers are located outside of the CT scan region 710. Asurgical field 750, the area where the invasive procedure will occur, islocated within the perimeter created by radio-opaque markers 730. Theactual distances of the radio-opaque and active markers relative to eachother is measured from a high-precision laser scan of the calibrationframe. Further, active markers are also placed on the robot (not shown).

The calibration frame 700 is mounted on the patient's skin beforesurgery/biopsy, and will stay mounted during the entire procedure.Surgery/biopsy takes place through the center of the frame.

When the region of the plate with the radio-opaque markers 730 isscanned intraoperatively or prior to surgery in, for example, a computedtomography (CT) scanner, the CT scan contains both the medical images ofthe patient's bony anatomy and spherical representations of theradio-opaque markers 730. Software is used to determine the locations ofthe centers of the spheres relative to the trajectories defined by thesurgeon on the medical images.

Because the system knows the positions of the trajectories relative tothe radio-opaque markers 730, the positions of the radio-opaque markers730 relative to the active markers 720, and the positions of the activemarkers 720 on the calibration frame 700 relative to the active markerson the robot (not shown), the system has all information necessary toposition the robot's end effector relative to the defined trajectories.

One aspect of the software disclosed herein is a unique algorithm forlocating the center of the above-described spheres that takes advantageof the fact that a CT scan consists of slices typically spaced 1.5 mm ormore apart in the z direction but sampled with about 0.3 min resolutionin the x and y directions. Since the diameter of the radio-opaquespheres is several times larger than this slice spacing, different zslices of the sphere will appear as circles of different diameters oneach successive xy planar slice. Since the diameter of the sphere isdefined beforehand, the necessary z position of the center of the sphererelative to the slices can be calculated that achieves the given set ofcircles of various diameters. This algorithm provides, for example, thecenter of a large sphere more precisely than other methods could findthe center of a sphere that is closer in diameter to the slicethickness.

To provide further illustration of how the calibration plate worksaccording to an embodiment of the invention, the steps of a closedscrew/needle insertion procedure utilizing a calibration frame isdescribed. First, a calibration frame 700 is attached to the patient'sskin in the region at which surgery/biopsy is to take place. Next, thepatient receives a CT scan either supine or prone, whichever positioningorients the calibration frame upward. Thereafter, the surgeonmanipulates three planar views of the patient's CT images with rotationsand translations. The surgeon then draws trajectories on the images thatdefine the desired position and strike angle of the end effector.

The robot then will move to the desired position. If forceful resistancebeyond a pre-set tolerance is exceeded, the robot will halt. The robotholds the guide tube at the desired position and strike angle to allowthe surgeon to insert a screw or needle. If tissues move in response toapplied force or due to breathing, the movement will be tracked byoptical markers and the robot's position will automatically be adjusted.

As a further illustration of a procedure using an alternate guidancesystem, the steps of an open screw insertion procedure utilizing anoptical guidance system is described. After surgical exposure, a smalltree of optical markers is attached to a bony prominence in the area ofinterest. Calibration procedures standard for image guidance are used toestablish the anatomy relative to the optical tracking system andmedical images.

The surgeon manipulates three planar views of the patient's CT imageswith rotations and translations. The surgeon then draws trajectories onthe images that define the desired position and strike angle of the endeffector.

The robot moves to the desired position. If forceful resistance beyond apre-set tolerance is exceeded, the robot will halt. The robot holds theguide tube at the desired position and strike angle to allow the surgeonto insert a screw. If tissues move in response to applied force or dueto breathing, the movement will be tracked by optical markers and therobot's position will automatically be adjusted.

From the foregoing it will be observed that numerous modifications andvariations can be effectuated without departing form the true spirit andscope of the novel concepts of the present invention. It is to beunderstood that no limitation with respect to the specific embodimentsillustrated is intended or should be inferred. The disclosure isintended to cover by the appended claims all such modifications as fallwithin the scope of the claims.

What is claimed is:
 1. A system for performing a medical procedure, comprising: a robot comprising: an instrument; an effectuator element, the effectuator element configured to securely hold the instrument at a desired position; a motor assembly that is configured to move the effectuator element in each one of the x, y and z directions; and a control unit that is operatively coupled to the robot, wherein the control unit is configured to transmit signals to the robot to cause the motor assembly to selectively move the effectuator element along the x, y and z directions, the control unit being configured (i) to calculate a position of a transmitter affixed to the instrument by analysis of signals emitted by the transmitter (ii) display a position of the instrument with respect to a patient's body based on the calculated position of the transmitter and (iii) to control actuation of the motor assembly, wherein the transmitter is affixed at a desired location of the instrument and the control unit is configured to selectively energize the transmitter to cause at least a portion of the instrument to move in a desired direction.
 2. The system of claim 1 wherein the instrument is optically guided.
 3. The system of claim 1 wherein a position signal is generated to provide the position of the instrument.
 4. The system of claim 3 wherein the position signal is generated with one or more of magnetic sensors, capacitive sensors, and optical sensors.
 5. The system of claim 1 wherein the position of the surgical instrument is determined relative to a reference position.
 6. The system of claim 1 wherein the signals transmitted from the transmitter are radiofrequency (RF) signals.
 7. The system of claim 1, wherein the effectuator element is configured to have three transmitters evenly radially distributed around the effectuator element.
 8. The system of claim 7, wherein the effectuator element is configured to have three transmitters affixed to a distal end thereof.
 9. The system of claim 8, wherein the three transmitters are located on a leading edge of the effectuator element.
 10. A system for performing a medical procedure, comprising: a robot comprising: an instrument an effectuator element, the effectuator element configured to securely hold the instrument that is to be positioned at a desired location; a motor assembly that that is configured to move the effectuator element in each one of the x, y and z directions and a control unit that is operatively coupled to the motor assembly, the control unit supplying signals to the robot to cause the motor assembly to selectively move the effectuator element along the x, y and z directions, the control unit being configured (i) to calculate the position of a transmitter affixed to the instrument by analysis of signals emitted by the transmitter (ii) display a position of the instrument with respect to a patient's body based on the calculated position of the transmitter, and (iii) to control actuation of the motor assembly wherein the transmitter is affixed at a desired location of the instrument and the control unit is configured to selectively energize the transmitter to cause at least a portion of the instrument to move in a desired direction.
 11. The system of claim 10 wherein the instrument is optically guided.
 12. The system of claim 10 wherein a position signal is generated to provide the position of the instrument.
 13. The system of claim 12 wherein the position signal is generated with one or more of magnetic sensors, capacitive sensors, and optical sensors.
 14. The system of claim 10 wherein the position of the surgical instrument is determined relative to a reference position.
 15. The system of claim 10, wherein the transmitter generates a radiofrequency (RF) signal.
 16. The system of claim 10, wherein the effectuator element is configured to have three transmitters evenly radially distributed around the effectuator element.
 17. The system of claim 16, wherein the effectuator element is configured to have three transmitters affixed to a distal end thereof.
 18. The system of claim 17, wherein the three transmitters are located on a leading edge of the effectuator element. 